A typical wireless communication network includes a number of base stations each radiating to provide one or more coverage areas in which wireless client devices (WCDs) such as cell phones, tablet computers, tracking devices, embedded wireless modules, and other wirelessly equipped devices, can operate. In turn, each base station could be coupled with network infrastructure that manages service of WCDs and that provides connectivity with one or more transport networks such as the public switched telephone network (PSTN) and/or the Internet. With this arrangement, a WCD within coverage of a base station may engage in air interface communication with the base station and could thereby communicate via the base station with various remote network entities or with other served WCDs.
Such a network could operate in accordance with a particular radio access technology, with communications from the base stations to WCDs defining a downlink or forward link and communications from the WCDs to the base stations defining an uplink or reverse link. Examples of existing radio access technologies include, without limitation, Long Term Evolution (using Orthogonal Frequency Division Multiple Access (OFDMA) on the downlink and Single Carrier Frequency Division Multiple Access (SC-FDMA) on the uplink), Code Division Multiple Access (CDMA) (e.g., 1×RTT and 1×EV-DO), Global System for Mobile Communications (GSM), and Wi-Fi, among others. Each technology may define its own procedures for managing communications with WCDs.
In accordance with the radio access technology, each base station coverage area could have a coverage area ID and could operate on one or more carrier frequencies. Further, each coverage area could define a number of channels or other resources for carrying specific communications between the base station and WCDs. For instance, on the downlink, certain resources may be used to carry a pilot signal or reference signal that WCDs can detect and measure as a basis to evaluate coverage, and other resources may be used to carry other control signaling and bearer data communications from the base station to WCDs. And on the uplink, certain resources may be used to carry access requests from WCDs, and other resources may be used to carry other control signaling and bearer data communications from WCDs to the base station.
When a WCD first powers on or enters into coverage of such a network, the WCD could search for a strongest coverage area in which to operate and could then engage in signaling with the base station that provides that coverage area, and in turn with the network infrastructure, to register for service in that coverage area. In turn, the WCD could then be served by the base station in a connected (e.g., active) mode or in an idle mode.
In the connected mode, the WCD would have a radio-link-layer connection with the base station, through which to engage in calls and/or other bearer communication. Whereas, in the idle mode, the WCD may lack a radio-link-layer connection but could “idle” in the base station's coverage area, monitoring the air interface for any page messages destined to the WCD, and the WCD and base station could engage in signaling when necessary to re-establish such a connection. Thus, if the network has a call or other bearer communication to provide to the WCD, the base station could broadcast a page message destined to the WCD, and the WCD could detect that page message and responsively engage in signaling with the base station to re-establish a radio-link-layer connection so as to then receive the communication. And if the WCD has a call or other bearer communication to initiate, the WCD could similarly engage in signaling with the base station to re-establish a radio-link-layer connection and could then provide that communication.
In both the connected mode and the idle mode, a WCD may also engage in handover between coverage areas from time to time. For instance, as the WCD moves from one coverage area to another and/or as circumstances otherwise change, the WCD may experience a threshold decrease in signal strength from its serving coverage area and a threshold increase in signal strength from a target coverage area. When this happens in the connected mode, the WCD may responsively provide a measurement report to its serving base station, and the base station and network infrastructure may then coordinate transition of the WCD to be served by the target coverage area. Whereas, when this happens in the idle mode, the WCD may autonomously transition to idle in the target coverage area, monitoring the air interface of the target coverage area for any page messages destined to the WCD, and engage in signaling when necessary to transition to the connected mode in the target coverage area.
To facilitate efficient paging of idle-mode WCDs given their possible handover between coverage areas, the coverage areas of a typical wireless communication network could be grouped into clusters defining paging zones (or tracking areas), with each paging zone having an associated zone ID. Further, the base station of each coverage area could be configured to broadcast the coverage area's associated zone ID, and each WCD could be configured to read the broadcast zone ID of the coverage area in which it operates. And the network infrastructure could include a paging controller to track WCDs' current paging zones and to accordingly manage paging.
In practice with this arrangement, when a WCD registers for service in given coverage area, the WCD and paging controller could record the coverage area ID and the associated the zone ID of the WCD's current serving coverage area. In turn, if the WCD hands over between coverage areas while in the connected mode, the WCD and paging controller could update their records to indicate the coverage ID and associated zone ID of the WCD's new serving coverage area. Further, if the WCD hands over between coverage areas while in the idle mode, the WCD could check to see if the zone ID of the new serving coverage area is different than the zone ID of the previously serving coverage area. And if the zone ID is different, then the WCD could responsively engage in signaling with the base station of the new coverage area to re-register for service in the new coverage area, and the WCD and paging controller could update their records to indicate the coverage ID and associated new zone ID of the WCD's new serving coverage area.
When the network infrastructure then has a communication to provide to an idle-mode WCD, the paging controller could engage in a zone-based paging process, in which the paging controller engages in a series of page attempts with progressively increasing coverage range to account for the possibility that the WCD has moved away from its currently recorded coverage area but has not yet entered into a new paging zone. In particular, the paging controller could transmit an initial (ordinal first) page to the WCD in the WCD's currently recorded serving coverage area. And absent a response to that initial page, the paging controller could then transmit a next page to the WCD in a somewhat wider region encompassing the WCD's currently recorded serving coverage area and perhaps each adjacent coverage area. And still absent a response from the WCD, the paging controller could then transmit a next (possibly final) page to the WCD in all of the coverage areas of the WCD's currently recorded paging zone, which should hopefully result in a response from the WCD.
Advantageously, this process could thus help ensure efficient and successful paging of the WCD.